Aqueous cleaning compositions exhibit a tendency toward foaming because they contain surface active agents such as soaps, and synthetic detergents. In many instances, such cleaning compositions produce excessive foam and the user must use substances known as add anti-foaming agents or defoamers. Some defoamers such as silicones tend to interfere with the function of the cleaning compositions in that unwanted residues are left after the cleaners are wiped off while others are environmentally unacceptable because they are not biodegradable.
Alkyl polyglycosides are a class of nonionic surfactants that exhibit significantly higher foaming profiles than other nonionic surfactants, such as alcohol ethoxylates. In fact, it can be said that the foaming tendencies of alkyl polyglycosides more closely resemble those of anionic surfactants, such as alcohol sulfates, than the foaming tendencies of other nonionic surfactants. This higher foaming tendency makes the use of alkyl polyglycosides undesirable for many applications, e.g. cleaning-in-place for food processing plants, high pressure spray cleaning, bottle washing, floor cleaners and automatic dishwashing, wherein high levels of foam interfere with the cleaning and rinsing operation and reduce the efficiency of the operation.
Low foam nonionics, such as EO/PO block copolymers, can be used to reduce the foaming properties of alkyl polyglycoside surfactants, but these materials have undesirable properties, e.g. low biodegradability, relatively high aquatic toxicity and poor caustic compatibility.
Accordingly, there is a need for the development of defoamers that do not interfere with the cleaning ability of aqueous cleaning compositions and that are biodegradable, exhibit low aquatic toxicity and good caustic compatibility.